C++

参考

<memory>

类模板
<memory>

std::uses_allocator

template <class T, class Alloc> struct uses_allocator;
Uses allocator

Trait class that identifies whether T accepts an allocator convertible from Alloc.

它继承自 integral_constant，并根据Taccepts such allocator.

The unspecialized definition for this template inherits from true_type ifT::allocator_typeexists andis_convertible<Alloc,T::allocator_type>::valueis notfalse.

Classes that do not fill this requirement but still use an allocator shall specialize this template to derive from true_type if either
  • the last argument of a constructor has type Alloc.
  • or, the first argument of a constructor has type allocator_arg_t and the second argument has type Alloc.

模板参数

T
一个类型。
Alloc
An allocator type.

成员类型

Inherited from integral_constant
成员类型定义
value_typebool
类型true_type 或 false_type

成员常量

Inherited from integral_constant
成员常量定义
值是trueorfalse

成员函数

Inherited from integral_constant
operator bool
Returns value (public member function)

示例

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// uses_allocator example
#include <iostream>
#include <memory>
#include <vector>

int main() {
  typedef std::vector<int> Container;
  typedef std::allocator<int> Allocator;

  if (std::uses_allocator<Container,Allocator>::value) {
    Allocator alloc;
    Container foo (5,10,alloc);
    for (auto x:foo) std::cout << x << ' ';
  }
  std::cout << '\n';
  return 0;
}

输出
10 10 10 10 10


另见

allocator_traits
分配器特性 (类模板)